In a semiconductor manufacturing process, a plurality of processing apparatuses have been used. For example, a processing apparatus, such as a plasma processing apparatus, has been widely used in a film forming process or an etching process of objects to be processed, such as semiconductor wafers or glass plates. For example, in the plasma processing apparatus, process gas introduced into an airtight processing chamber is converted into plasma, and then the surface of an object to be processed, for example, a semiconductor wafer, is plasma-processed. Therefore, during the repetition of the plasma-processing, a reaction product is generated and attached to an inner wall of the processing chamber, thus delicately varying the status of the plasma. Since such a variation of the plasma status influences the results of processing the wafer, e.g., etching the wafer, the process results should be closely monitored so as to consistently execute a stable process.
Due to the above reason, for example, test wafers are manufactured in advance and an etching process is periodically executed with respect to each of the test wafers, so that the status of a processing apparatus after etching each of the wafers may be examined on the basis of the process results (for example, the quantity of abrasion of the test wafers) obtained through the etching process.
However, in order to examine the status of the processing apparatus on the basis of the test wafers, it is necessary to manufacture a great number of test wafers. Moreover, since a large number of test wafers should be processed using the processing apparatus and respective process results thereof should be measured, there is a problem in that many processes and a lot of time are required for the manufacturing of test wafers and the measurement of process results.
Meanwhile, as disclosed in Japanese Patent Laid-open Publication No. H10-125660, a process monitoring method for a plasma processing apparatus has been proposed. In this method, after a modeling equation used to correlate an electrical signal, in which plasma status is reflected, with plasma process characteristics is set up using a test wafer, a detected value of an electrical signal obtained when an actual wafer is processed is applied to the modeling equation, thus accurately predicting the plasma process characteristics.
However, the above process monitoring method is advantageous in that the plasma processing characteristics can be predicted, but problematic in that the data, such as the detected value of an electrical signal used when setting up the modeling equation, may not occasionally be sufficient to perform a high accuracy prediction, so that further improvements are required.
For example, among the data used at the time of setting up the modeling equation, data contributing toward deteriorating a prediction value with respect to an actual measurement value may exist. In this case, if all data are used without the selection of data proper for setting up the modeling equation, prediction results may occasionally be worse.